Feature request: A function to sort everything #115

An OpenAPI spec contains a bunch of lists where the ordering is not significant. It would be handy to have a function that sorts all the order-insensitive lists within an OpenApi to create a somewhat normalized version of a specification for use in comparisons. For example, we have snapshot test to ensure that our spec generated by servant-openapi3 is right, and it would be nice if insignificant changes to ordering were not reflected in the snapshot.